I don't think SE will position servers in every region. I don't think it has much to do much with segregating the playerbase so much as their core development team is in Japan and want to be close to their hardware.

As far as people talking about latency and such, anyone in Japan will always have an edge against anyone not there since they are closer to the servers. In Japan they probably have a 10-20ms ping. I live in Arizona and I get about a 50ms ping to the server, and it gets worse the further east you go. That's why Europeans notice lag the most; they're getting 200ms (or worse) pings to the server. This is all networking related and it won't be better unless routes to the server are better optimized. (which SE has no control over)